Crouching behind bushes left bare by the winter, the camouflaged fighters waited in tense expectation on the bleak Caucasian mountain side.

Casually flicking his cigarette into the mud, the Chechen loyalist commander raised his radio towards his mouth and barked an order. On the ridge above us a modified anti-aircraft gun opened fire, directing its staccato bursts towards Tazan Kala, a tiny settlement and rebel stronghold nestled in the isolated foothills of southern Chechnya.

Seconds later, automatic gunfire punctuated by the crunch of mortars echoed through the mountains.

From their positions across the valley, the rebels sporadically began to return fire but, outnumbered and outgunned, theirs seems a hopeless cause. Drawn up against them were members of the Eastern Battalion, a Chechen special forces unit that once fought alongside the separatists, but now pledges allegiance to Moscow.

For these hardened fighters, this was just another battle. In the past few years they have become the vanguard of President Vladimir Putin's war in Chechnya, a campaign so secret it is officially no longer being fought.

The appointment was accompanied by a flurry of declarations from the Kremlin that the war was over and the last of the rebels had surrendered.

But after witnessing the battle for Tazan Kala, The Daily Telegraph can reveal compelling evidence that a secret war is underway, and could last for years.

Sitting in his heavily fortified base in Chechnya's second city of Gudermes on the eve of the battle, the tracksuit-clad commander of the Eastern Battalion claimed there were well over 1,000 separatist rebels and foreign Islamic militants entrenched in the mountains.

"The war is not over," said Colonel Sulim Yamadayev, Chechnya's second most powerful loyalist warlord after Ramzan Kadyrov.

"The war is far from being over. What we are facing now is basically a classic partisan war and my prognosis is that it will last two, three, maybe even five more years."

In an attempt to stem the steady trickle of Russian casualties, 11,000 of whom are estimated to have died since the second Chechen war erupted in 1999, Mr Putin has made Yamadayev his main battlefield commander.

That in itself seems odd. Yamadayev and the vast majority of his men, known in Chechnya as Yamadayevtsi, fought alongside the rebels in the first Chechen war, waged between 1994 and 1996.

In that campaign, Yamadayev was even a close ally of Shamil Basayev, Russia's most wanted terrorist, who claimed responsibility for the Beslan school siege in 2004 among numerous atrocities.

He was killed in an explosion last year. Now a close Kremlin ally, personally decorated by Mr Putin, Yamadayev says he changed sides after Islamic extremists infiltrated and, despite being a small minority, then began to dominate the rebel movement. Critics say he defected after being offered large financial inducements.

Whatever is the case, Mr Putin has got what he wants. The rebels have been stripped of much of their support base, while the president now sends in Chechen proxies to fight his war for him.

Their faces wizened from over a decade in the battlefield, the Eastern Battalion fighters are a much tougher proposition for the rebels than the poorly equipped, unmotivated and corrupt Russian soldiers - who often used to sell their weapons to the enemy - that they fight alongside.

The battle plan at Tazan Kala was meticulously executed. The rebels, taken by surprise, found themselves surrounded on three sides. "The artillery will smoke them out of their base," said Magomet, commander of the Eastern Battalion company in the notoriously volatile town of nearby Vedeno. "Now we will lure them towards us. They are walking into a trap."

A bus wound its way slowly through the hills nearby. We paused briefly to watch the faces of its mostly female passengers, pressed against the windows in terror, and then moved on. It is civilians who have made up the vast majority of casualties in the two Chechen wars, which have claimed some 200,000 lives according to conservative estimates.

"Allahu Akhbar [God is great]," shouted Magomet as his radio crackled into life. "We are coming under fire in this area all the time. There are a lot of bad guys around here - this is Wahabi Central," he said, referring to the Islamists who have long fought in the conflict and follow the puritanical Wahabi strain of Sunni Islam.

We reached a bend in the river and before us lay the first signs of success: the corpses of four rebels scattered across the river bank.

Two appeared to have been finished off with a bullet to the back of the head. A third had blown himself up with his own grenade in an attempt to avoid capture.

The Yamadayevtsi, who often like to severe the heads of their dead victims, have a brutal reputation when it comes to prisoners. Human rights activists say captive rebels, as well as innocent civilians who run foul of the Eastern Battalion, are frequently sexually abused and then tortured to death.

Yamadayev insists that the rebels have to be dealt with uncompromisingly.

But as the fighters strip the corpses of ammunition, gunfire suddenly erupts around us. I watched as a rebel in black blazed away with his gun from behind a tree. But 15 minutes later it was all over - the rebels had retreated. Four had been killed, but unlike Mr Putin, apparently, the special forces know there are plenty more rebels lurking in southern Chechnya's sinister mountains.